Cl-bearing lizardite in metamorphosed kimberlites from the Udachnaya Vostochnaya Pipe,Yakutia |
| |
Authors: | E L Sokolova E M Spiridonov S A Vorob’ev |
| |
Institution: | (1) Department of Geology, Lakehead University, Thunder Bay, ON P7B 5E1, USA |
| |
Abstract: | Anhydrite-bearing dolomites and kimberlites from the contact zone of the Udachnaya Vostochnaya pipe, northern part of the
Eastern Siberian Platform, were affected by low-grade metamorphism to the zeolite facies. The kimberlites are serpentinized
and carbonatized and contain metasomes of anhydrite and saponite pockets. Twenty lizardite pseudomorphs after olivine (Fo
91–82) in the kimberlites were examined on an electron microprobe. The lizardite is rimmed by saponite and contains dolomite, calcite,
magnetite, and anhydrite inclusions. Lizardite in the central parts of the pseudomorphs contains 1.5–1.9 wt % Cl and 6–9 wt
% Fe2O3, and this mineral in the outer portions of the pseudomorphs bears 0.7–1.0 wt % Cl and 2–6 wt % Fe2O3 (the paper presents nine microprobe analyses and images showing the distribution of Cl, Mg, Al, Si, S, Ca, Ti, and Fe obtained
in characteristic X-ray radiation). The amounts of Fe3+ in octahedrally and tetrahedrally coordinated sites of the Cl-bearing lizardite are roughly equal. Cl was borrowed in the
course of serpentinization from the host Early Paleozoic evaporites and brines contained in them. The Cl concentration in
our lizardite from the metamorphosed kimberlites from the Eastern Siberian Platform (continental lizardite) is much higher
than the Cl concentration in oceanic lizardite from serpentine replacing peridotites (0.03–0.2 wt % Cl). This is likely explained
by differences in the Cl concentrations in the metamorphic fluids, their salinity (3% for oceanic water and 65% for brines
in the platform cover). |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|